That means Tricare users will newly be able to fill their prescriptions off base at Walgreens pharmacies without paying out-of-network rates, and CVS users will need to find a new pharmacy or pay unsubsidized rates for their medications.

The change takes effect Dec. 1, officials said. It will impact all beneficiaries, including Tricare for Life users and military retirees. The network will add about the 8,000 Walgreens stores and lose more than 9,600 CVS pharmacies.

“Starting Dec. 1, 2016, Walgreens pharmacies will join the Express Scripts, Inc. network serving TRICARE beneficiaries across the United States,” Tricare officials said in a news release. “Additionally on Dec. 1, CVS pharmacies, including those in Target stores, will leave the network.”

More than 58,000 pharmacies are in the Tricare network, according to an Express Scripts fact-sheet. As of Dec. 1, that number will drop to 57,000 according to the release. Tricare currently serves about 9.4 million beneficiaries.